The biggest bang since the big bang

May 8, 1998

A gamma-ray burst observed by astronomers on December 14 last year was,
for a few seconds,
as luminous at the rest of the entire universe. Indeed,
according to George Djorgovski of the California Institute of Technology,
"the burst created in a region about a hundred miles across conditions like those about one millisecond after the Big Bang." The discovery of the burst,
its afterglow at X-ray,
infrared and optical wavelengths,
and the possible identification of a very distant host galaxy for the burst are the subject of three papers in the May 7 issue of Nature. However the cause of this so-called hypernova explosion is still a mystery to astronomers.

The 50 second burst,
known as GRB971214,
was detected by the
two satellites.
The Italian/Dutch BeppoSAX satellite gave the
precise position of the
blast,
while NASA's Compton Gamma Ray Observatory measured its brightness.
Further observations at different wavelengths by a collection of ground and
space-based telescopes measured the
distance to the
optical counterpart of the
burst to be 12 billion light years.
The Hubble Space Telescope then provided a more detailed image of the
'host' galaxy.
The vast distance to the
galaxy,
plus the
brightness of the
burst,
implies an enormous energy release - several hundred times that of a supernova,
until now the
most energetic phenomenon known in the
universe.
Even more energy may have been released as neutrinos and
gravity waves.

"Most of the theoretical models proposed to explain these bursts cannot explain this much energy,
" said Shrinivas Kulkarni of Caltech,
a co-author on two of the papers. "However,
there are recent models,
involving rotating black holes,
which can work. On the other hand,
this is such an extreme phenomenon that it is possible we are dealing with something completely unanticipated and even more exotic."